Simultaneous blueing and dustproofing of solid carboniferous fuels



Patented Dec. 9, 1952; "i1

UNITED STATES 2,62l,ll5

. TENT OFHCE SIMULTANEOUS BLUEING AND DUSTPROOF- ING OF SOLIDCARBONIFEROUS FUELS No Drawing. Application June 21, 1950, Serial No.169,524

Claims.

This invention relates to oil-in-water emulsions comprising adustproofing oil and ultramarine, to the application of these emulsionsto solid Carboniferous fuels in particulate form, and to such fuelswhich have been treated with said emulsions.

Hereinafter said fuels, which include bituminous coal, anthracite coal,bituminous coke, and briquetted fuels comprising these fuels or mixturesthereof, will be generically referred to as coal.

In the past a demand has arisen for a blue coal, that is, coal whichwhen viewed en gros by the ordinary consumer under ordinar conditionshas a blue appearance or mass tone. At the present time the color bluehas acquired a secondary meaning and is a very valuable trade-mark.

The problem of blueing coal was solved from the optical point of view byU. S. Patents 2,129,901 and 2,129,902, which disclosed a process fordepositing a brilliantly blue ferro-ferricyanide salt on the coal. Thisprocess, however, required relatively costly chemicals, and careful andcontinuous technical control both of the chemicals and of the coal.

To solve the problem of costs it was proposed to pigment coal directlywith the bright blue ultramarine pigment of commerce. When this pigmentwas applied to coal, however, it washed 'ofi readily when sprayed withwater. Subsequent ly, the discovery was made by Dieterle (U. S.2,323,748/9) that ultramarine could be coated with a water-insolublesoap or with a free organic acid, that this ultramarine could bedispersed in water, and that when this ultramarine was sprayed on coal,it was transformed irreversibly into an adherent blue pigmentation whichwas water-repellent and which completely met the specifications of thetrade. The Dieterle process of coloring coal is amazingly cheap andefficient. Only a few ounces of ultramarine are n eded to pigment a tonof coal, and the process is conducted almost automatically by commonlabor without the use of any special or costly equipment. 7 I

Since the war the greatly increased price of anthracite coal, bituminouscoal, and coke, coupled with sharp consumer preference for oil andnatural gas, has made further improvements in the chara t r st c OI t ee olid fuels imp At the present time two of the most disadvantageouscharacteristics which coal possesses are (1) it freezes into a solidmass When wetted and then subjected to sub-freezing temperatures,thereby increasing handling costs; and (2) it develops large volumes ofdust when shot into the coal bin of the average consumer, therebyincreasing the work of the average housewife. A demand, therefore, hasarisen for a coal which is free from these characteristics.

It has long been and still is the general practice of coal retailers todrench coal with a hez vy spray of water immediately prior to deliveryof the coal to the ultimate consumer. While this spraying diminishes thetendency of the coal to raise clouds of drst when shot into thehouseholders bin, the eifectiveness of this water treatment disappearsin a few hours and thereafter the coal dusts just as readily as if ithad not been wetted. This practice of wetting down the coal isparticularly objectionable in that a large amount of water drains fromthe coal and collects in pools on the householders cellar floor.

In recent years, both of the above-noted disadvantageous characteristicsof ordinary coal, that is, coal which has not been blued, have beenlargely overcome by applying dustproofing oily liquids, hereinaftercalled dustproofing oils. Application of these oils at once permits thefuel to shed rain water, and dustproofs the fuel as well.

When such dustproofing oils were applied to coal pigmented withultramarine, however, the blue coloration of the coal instantly andsubstantially completely disappeared. As ultramarine has about the sameindex of refraction as that of the oils employed, this oiling caused theultra marine to lose its surface reflectivity andto'assume an apparentlyblack glossy color which was indistinguishable from the color of thecoal. As a result, the valuable secondary meaning of the blue colorationwas completely lost.

This masking or destruction of the tinctorial value of the ultramarineoccurred regardlessof Whether the dustproofing oil was applied to thefuel before or after application of the ultrama-i rine, and regardlessof whether the oil was applied as such, or as an aqueous emulsion.

The surprising discovery has now been made that when ultramarine isadded to an emulsion of a dustproofing oil of the oil-in-water type,

prepared as set forth below, and when an emulsion of this type issprayed on coal, the emulsion breaks in such a way that the oil and aportion of the ultramarine part company and that as a result sulficientultramarine having its brilliantly blue dry shade becomes visible on thesurface of the coal to impart a blue mass tone to the coal. It has beenfound that after the emulsion has broken and after the water containedin the emulsion has run from the thus pigmented coal, the coal has agenerally dust-proof and water repellent surface.

The above-described discovery as to the manner in which the emulsions ofthe present invention break could not have been predicted because whensprayed on ordinary steel test panels, these emulsions yield asubstantially continuous film of oil having a grimy appearance in whichthe color of the ultramarine is virtually completely masked.

This discovery could not have been predicted for the further reason thatit would have been expected that the ultramarine would run off with thewater. Ultramarine is an organophobic, hydrophilic pigment which has aselective affinity for water and which is normally readily wet thereby.

The reason for this behavior of the ultramarine emulsion isv not known,and it. is not intended to limit the present invention to any particulartheory of action.

More in. detail, according to the present invention, an emulsion is madeby dispersing a watersoluble organic anionic or non-ionic emulsifyingagent, a dustproofing oil, and ultramarine with at least sufficientwater to form an oil-in-water emulsion. This emulsion is then sprayed oncoal. It is immaterial from the point. of view of result as to how thisemulsion is formed and the constituents may be added in any sequence tothe water.

Additional pigments may be added to the emulsions of the presentinvention to vary the color thereof. For example, addition of chromeyellow will give an emulsion having a greenish tint.

As emulsifying agent a preformed soap may be used. However, it ispreferred to form the soap in situ by reaction of a solution of apredetermined amount of a water-insoluble, soap-forming organic acid anda saponifying agent. This agent or base may be the hydroxide, carbonateor bicarbonate of sodium, potassium or ammonium, or morpholine,triethanolamine, triethylamine, tetramethyl ammonium hydroxide orpiperidine, as is well-known in the art. The acid may be any of theordinary cheap soap-forming acids such as oleic, palmitic, stearic ortall oil fatty acids. In addition, undecylenic acid, coconut oil fattyacids, castor oil fatty acids, soya oil fatty acids, abietic acid,naphthenic acids, perilla oil fatty acids, and neatsfoot oil fatty acidsmay be used in proportional amounts. I prefer to use the cheapest acids,and for this purpose tall oil acids, oleic acid and stearic acid havebeen found very suitable. The proportion of the soap-forming acid shouldbe sufiicient that when this acid is saponified, the oil and theultramarine are emulsified with only slow stirring. An amount of acidranging from 3% to 20% of the weight of the oil and of the ultramarineis usually suiiicient for this purpose. I prefer to use about 4% to 9%.With this proportion, the emulsion begins to separate within a fewminutes when stirring is halted, a thin layer of oil forming on the,surface, and this is desirable.

It is surprising that the. proportion of the saponifying base added isnot critical. When less is added than the amount necessary to convertall the acid to the soap, the unreacted acid simply dissolves in andbecomes part of the oil phase. For example, when 15% of acid is addedbased on the weight of the ultramarine and dustproofing oil and onlysuflicient saponifying agent is added to saponify /3 of said acid, thebalance of the acid dissolves in the dustproofing oil and does notproduce any harmful effect. When more than the stoichiometricalproportion of base is added, the excess serves to stabilize theemulsion. Since the soap-forming acids are usually more expensive thanthe dustproofing oils I prefer to add a substantial excess of the base,which excess may be two hundred or three hundred percent. I prefer to.add about 275 percent of the stoichiometrical proportion of the base,particularly when the emulsion is to be applied in freezing weather.

This invention is not limited to the use of soap as a dispersing agent.Any other of the numerous anionic or non-ionic dispersing agents foremuls fying dustproofing oils may be used, as is wellknown in the art.Among these are: alkyl benzene sodium sulfonate (UltraWet 30E), sodiumlignin sulfonate, a naphthalene sulfonic acidformaldehyde condensationproduct (Tanak L), an alkylated aryl polyether alcohol (Triton N-lOO), apolyethylene ether of a long chain fatty acid (Emulfor ON), soda ash anddistilled tall oil (Acintol D)-. The first five require vigorousagitation and therefore are not preferred. The last mentioned agent,however, gives excellent results with slow stirring. Anionic dispersingagents are preferred, and cationic emulsifying agents should be avoided.

In any event, suflicient emulsifying agent should be present to permitformation of an emulsion which is apparently stable on slow stirring andwhich forms a thin film of oil within two minutes when stirring ishalted.

It is a very surprising advantage of the present invention that, asatisfactorily adherent pigmentation results when ordinary, untreated,commercial ultramarine is used. This discovery was unexpected becausewhen a water dispersion of ordinary, untreated ultramarine is sprayed oncoal, the deposited ultramarine washes 01f readily after drying, and theDieterle ultramarine, described above, was produced to overcome thishigh lack of permanence. No soap insolubilizing agent or acid is presentin the instant process, and it therefore could not have been predictedthat when ordinary ultramarine is emulsified as set forth below, theultramarine acquires a sufficient degree of adhesiveness necessary forpractical commercial use. The reason for this remarkable improvement isnot known.

It is an additional surprising feature of the present invention thatDieterles ultramarines may also be used. It could not have beenpredicted that these Dieterle ultramarines Would not be preferentiallyWet by the dustproofing oils, or that the tinctorial value of theDieterle ultrama-rines would not be masked by the dustproofing oil.

The ratio of water to the soap, the dustproofing oil, and the bluepigment should be ample to insure formation of a blue, perfectly fluidoil-inwater emulsion, which begins. to break when allowed to stand fortwo minutes. Preferably the weight of the water is about 0 0f the Weightof the materials therein. When this proportion of water is used, theemulsion breaks rapidly on the coal, and GXCQSS Of Water does no harm.If

this proportion of water is reduced by more than 50% uneconomicallythick deposits of ultramarine will result, and pronounced masking of thecolor of the pigment will again become apparent. This materiallyincreases the cost of attaining satisfactory pigmentation withoutproducing any corresponding advantage, as it is only necessary that theweight of the ultramarine on the coal be not less than about 0.00005 andnot more than about 0.00025 of the Weight of the coal.

This invention is not limited to any particular dustproofing oil. It isa surprising advantage of the present invention that under theconditions employed herein ultramarine remains unwetted by these diverseexamples of which are oils, cyclic hydrocarbons including hydrocarbonnaphthenic oils, straight chain hydrocarbon oils including diesel oil,automotive lubricating oils, oily aryl esters including dibutyl and thelower alkyl phthalates, and vegetable oils, such as linseed oil andcottonseed oil have an index of refraction which is nearly the same asthat of ultramarine (1.55). The index of refraction of most of theseoils is within the range 1.35-1.6, and some oils have indices ofrefraction as high as 1.75. They do not freeze under ordinary winterconditions and have a very low rate of volatilization. The preferred oilis Acme Oil B, a straw-colored, very fluid hydrocarbon naphthenic oilboiling above 200 C. and having a specific gravity of 0.900. Its indexof refraction is about 1.5 at 25 0. Not more than about 1.5 parts byweight of oil should be used per part of ultramarine. Substantiallyincreasing the proportion of oil dims the final blue coloration, and useof a lesser proportion of oil merely yields a coal of reducedanti-dusting properties. Good results are obtained when 1.0-1.4 parts ofdustprofing oil are used per part of ultramarine.

It is advantageous to wash the coal before it is sprayed with theemulsions of the instant invention to prewet the surface of the coal andto wash the dust therefrom, but it is an advantage that it is notnecessary to do so.

In commercial utilization the emulsion is continuously sprayed over thecoal as it enters the cars or trucks for shipment at a predeterminedrate such that the coal, when dry, has a blue mass tone. Generally, thisrate is between about 0.1 and 0.5 lb. and preferably 0.4 lb. ofultramarine per ton of coal. When the percentage of dustproofing oil inthe emulsion is high as compared with the percentage of ultramarine, theweight of ultramarine per ton of coal should also be high. Substantiallyall the oil and ultrama rine are retained by the coal as it dries, and'arelatively clear solution of Water, containing some of the emulsifyingagent and any excess soda ash, drips from the cars.

Immediately upon completion of the spraying, the coal has a black andglossy appearance. It acquires a metallic blue coloration fairlyrapidly, and the bright blue, dry shade of the ultramarine does notbegin to appear for an hour or more. Development of maximum bluecoloration throughout the entire mass of the coal takes abouttwenty-four hours and often longer, depending on weather conditions.This delay is not disadvantageous because ordinarily the coal is intransit for several days before it reaches the householder.

When examined individually, the several lumps of coal are always seen tobe unevenly pigmented. In nearly every instance the maximum amount ofvisible blue is found on the surfaces which were horizontal during thedrying period. This is particularly noticeable in the case of anthracitecoal, which has numerous broad, glassy facets. With anthracite, maximumcoloration is usually found on the crevices which were horizontal duringthe drying period. A blue of lesser or metallic brilliance is found onthe broad planes and very little blue is precipitated on the moresharply inclined facets. Distinct coloration, however, may be exhibitedeven by the latter facets. The oil tends to collect on the lowersurfaces of the particles of the fuel.

Throughout the entire mass, certain of the lumps of the coal appear tobe nearly completely uncolored. This is not disadvantageous becausesufficient blue is present in other lumps to give the entire mass itscharacteristic blue appearance.

Bituminous coal and coke have very irregular surfaces and are free fromthe broad, glassy facets characteristic of anthracite coal. As a result,the vertical surfaces of these two fuels are usually more easilycolored, which often makes possible a slight reduction in the proportionof ultramarine which must be present to blue these fuels.

It is frequently desired to apply the emulsions of the present inventionduring freezing weather, and for this purpose the emulsions whichcontain a large percentage of soda ash are preferred.

The following examples illustrate preferred embodiments of the inventionand are not in limitation thereof. Parts are by weight unless otherwisenoted.

Eccample 1 Ten parts of soda ash are dissolved in 900 parts of water,and 15 parts of red oil (oleic acid) are dissolved in parts of Acme OilB (Atlantic Refining 00.), a straw-colored, very fluid, high boiling,cyclized hydrocarbon of the naphthenic type having a specific gravity of0.900 and an index of refraction of about 1.4965. The oil is thenstirred into the soda ash solution. An emulsion forms immediately whichpersists with only slight stirring. To this emulsion are added '72 partsof untreated ordinary ultramarine blue. With continued stirring, abright blue emulsion results which begins to break within two minuteswhen allowed to stand. This emulsion when sprayed on washed anthracitecoal, bituminous coal and bituminous coke at the rate of 0.4 lb. ofultramarine per ton of fuel, forms a distinctively blue product ofmarkedly reduced dusting characteristics. The visible ultramarineappears to be concentrated in the crevices. After two to four hours,when viewed from a distance, the coal is seen to have a blue mass tone.The blue is not noticeably washed off by the fall of heavy rain.

Example 2 Example 1 is repeated, the ultramarine, however, being addedto the soda ash solution. An emulsion results which has the sameproperties as the emulsion of Example 1.

Example 3 Example 1 is repeated, the ultramarine, however, being addedto the oil-oleic acid mixture. An emulsion results which has the sameproperties as the emulsion of Example 1.

7 Examples 4-9 The procedure of Example 1 is repeated using however, thefollowing proportions of the materials. In each instance 1000 parts ofwater is used.

Acid Example fig? Oil Name Parts l Acme Oil B.

Emulsions result which have substantially the same properties as theemulsion of Example 1. Satisfactory blueing occurs when these emulsionsare sprayed on coal at the rate of 0.4 lb. of'ultramarine.

Examples 1 0-14 The procedure of Example 1 was followed in which,however, the Acme Oil B was replaced with an equal weight of thefollowing oils:

Example Oil Hydrocarbon automotive engine oil SAE 40. Hydrocarbonautomotive engine oil SAE 50. Dibutyl phthalatc.

Raw linseed oil.

Nujol.

Example 15 The procedure of Example 1 .is followed using however anoleic acid coated ultramarine prepared according to the example ofDieterle U. S. 2,323,749. A similar emulsion results. When this emulsionis sprayed on coal, a pigmentation is obtained which is similar to thatobtained by Example 1 of the instant application and which is somewhatmore rain-resistant.

Example 16 Example 15 is repeated using however a sodium oleate coatedultramarine prepared according to Example 1 of Dieterle U. S. 2,323,748.A similar result is obtained.

Example 17 which comprises forming an oil-in-water emulsion from anultramarine, a water-insoluble oil having an index of refraction between1.35 and 1.75, a water-dispersible emulsifying agent selected from thegroup of anionic and non-ionic emulsifying agents, and water, said oilbeing in the dispersed phase and said ultramarine being in thecontinuous phase of said emulsion, and spraying said fuel with saidemulsion at a predetermined rate to deposit on said fuel a quantity ofultramarine amounting to at least 000005 of the weight of said fuel, theweight of said oil in said emulsion being not greater than about of theweight of said ultramarine and the weight of said water in said emulsionbeing at least about 250% of the weight of the other constituents ofsaid emulsion, and said emulsion being characterized by an instabilitywhich results in phase separation upon standing.

2. A process according to claim 1 wherein the fuel is anthracite coal.

3. A process according to claim 2 wherein the dust-proofing oil is acyclized hydrocarbon naphthenic dustproofing oil having an index ofrefraction of about 1.5 and a specific gravity of about 0.9.

4. A process according to claim 3 wherein the emulsifying agent is thesodium soap of talloil fatty acids.

5. A process according to claim 4 wherein the weight of water is about500% of the weight of the other constituents of the emulsion.

6. A process according to claim 5 wherein the weight of the oil is about1.0 to 1.4 of the weight of the ultramarine.

7. A process according to claim 6 wherein the emulsion is sprayed uponthe fuel at the rate of about 0.4 lb. of ultramarine per ton of fuel.

8. A process according to claim 1 wherein the fuel is bituminous coal.

9. A process according to claim 8 wherein the dustproofing oil is acyclized hydrocarbon naphthenic dustproofing oil having an index ofrefraction of about 1.5 and a specific gravity of about 0.9.

10. A process according to claim 9 wherein the emulsifying agent is thesodium soap of talloil fatty acids.

ROBERT BRUCE VAN ORDER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,902,886 Odell Mar. 28, 19331,928,214 Sperr Sept. 26, 1933 1,989,526 Powell Jan. 29, 1935 2,323,748Dieterle July 6, 1943 2,323,749 Dieterle July 6, 1943

1. A PROCESS FOR THE SIMULTANEOUS "BLUEING" AND DUSTPROOFING OF A SOLIDCARBONIFEROUS FUEL WHICH COMPRISES FORMING AN OIL-IN-WATER EMULSION FROMAN ULTRAMARINE, A WATER-INSOLUBLE OIL HAVING AN INDEX OF REFRACTIONBETWEEN 1.35 AND 1.75, A WATER-DISPERSIBLE EMULSIFYING AGENT SELECTEDFROM THE GROUP OF ANIONIC AND NON-IONIC EMULSIFYING AGENTS, AND WATER,SAID OIL BEING IN THE DISPERSED PHASE AND SAID ULTRAMARINE BEING IN THECONTINUOUS PHASE OF SAID EMULSION, AND SPRAYING SAID FUEL WITH SAIDEMULSION AT A PREDETERMINED RATE TO DEPOSIT ON SAID FUEL A QUANTITY OFULTRAMARINE AMOUNTING TO AT LEAST 0.00005 OF THE WEIGHT OF SAID FUEL,THE WEIGHT OF SAID OIL IN SAID EMULSION BEING NOT GREATER THAN ABOUT150% OF THE WEIGHT OF SAID ULTRAMARINE AND THE WEIGHT OF SAID WATER INSAID EMULSION BEING AT LEAST ABOUT 250% OF THE WEIGHT OF THE OTHERCONSTITUENTS OF SAID EMULSION, AND SAID EMULSION BEING CHARACTERIZED BYAN INSTABILITY WHICH RESULTS IN PHASE SEPARATION UPON STANDING.